1. Field of the Invention
The present invention relates to an IC card reading apparatus, and its related method, for reading out of, or writing in, an IC card in a noncontact manner.
2. Description of the Related Art
Use of IC cards has become increasingly popular as prepaid cards for public phones and railways, in place of magnetic cards.
The IC cards are categorized as two types, i.e., a contact and noncontact types, with the use of the noncontact type IC card (simply “noncontact IC card” hereinafter), which supplies the IC card with power wirelessly, having been in advance. The noncontact IC cards can be categorized as three types, i.e., a close coupling type, proximity type and vicinity type, depending on the communicable distance ranges. Widely used proximity type IC cards are ISO Type A and Type B (Type A and Type B according to ISO 14443).
A dedicated communication-use IC conforming to the Type A or Type B communication standards has already been developed, and an IC card reading and writing apparatus using the communication-use IC has been put in use.
A patent document, laid-open Japanese application publication No. 2002-170082, has disclosed a technique for detecting a signal intensity of a signal received from an IC card and changing wireless transmission power in accordance with the detected signal intensity.
While a dedicated apparatus capable of reading and writing an IC card conforming to a specific communication standard has been put in use as described above, a readout apparatus for IC cards conforming to different communication standards has not been accomplished.
The communication distance between an IC card and a read/write apparatus is different stemming from the differences in the communication standards or the specification and performance of a control part including the IC card, e.g., the communication distance of 2 cm for Type A, while 10 cm for Type B. Therefore, if a read/write apparatus is designed by using a communication-use IC confirming to a specific communication standard, it is possible to transmit a signal by a most optimal transmission power to an IC card conforming to a single communication standard, while it is not possible to transmit a signal by a most optimal transmission power to an IC card conforming to a different communication standard, hence having precluded accomplishment of an IC card reading apparatus that will be convenient for users when using IC cards conforming to various communication standards.